Boosting of data transmission

ABSTRACT

The invention concerns a method for boosting data transmission in a telecommunications system and a mobile communications system. The invention is characterised in that the telecommunications network uses at least on a part of the transmission path between the fixed station, e.g. a base transceiver station, and the transcoder unit speech coding at a lower transmission rate than the transmission rate of the speech coding used on the transmission path between the fixed station and the terminal equipment. The speech parameters received from the terminal equipment are converted for the speech coding method used on the transmission connection between the fixed station and the transcoder unit and vice versa. In the network transcoder unit it is possible to reconvert speech parameters received from the direction of the terminal equipment e.g. into speech parameters of the speech coding used on the transmission path between the terminal equipment and the fixed station.

FIELD OF THE INVENTION

[0001] This invention concerns a method of boosting data transmission ina telecommunications network.

BACKGROUND OF THE INVENTION

[0002] In FIG. 1 of the appended drawing a simplified Global System forMobile communications, a GSM system for short, is shown as a blockdiagram. The Network Subsystem, NSS, includes a mobile servicesswitching centre MSC which is connected to other mobile servicesswitching centres, and directly or through a Gateway Mobile ServicesSwitching Centre, a GMSC system interface the mobile network isconnected to other networks, such as a Public Switched TelephoneNetwork, PSTN, an Integrated Services Digital Network, ISDN, otherPublic Land Mobile Networks, PLMN, and packet switched public datanetworks, PSPDN, and circuit switched public data networks, CSPDN. Inthe mobile services switching centre MSC there are Network InterworkingFunctions, IWF, for matching the GSM network with the other networks.Through an A-interface the NSS network subsystem is connected to a BaseStation Subsystem, BSS, which includes base station controllers BSC,each one of which controls the base transceiver stations BTS connectedto them. The interface between the base station controller BSC and thebase transceiver stations BTS connected to it is an A bis interface. Thebase transceiver stations BTS for their part are connected over a radiopath with mobile stations MS across the radio interface. The operationof the whole system is monitored by an Operation and Maintenance Centre,OMC.

[0003] The mobile station MS sends speech or user data across the radiointerface on a radio channel at standard rates of e.g. 13 kbit/s or 5.6kbit/s. Speech coding is used in the speech transmission to achieve alower transmission rate than typically in telephone networks, wherebythe band width needed by the radio link on the radio path is reduced.The base transceiver station BTS receives the data of the trafficchannel and transmits it into the 64 kbit/s time slot of the PCM line.Into the same time slot, that is, channel, are also placed three otherfull-rate traffic channels of the same carrier wave, so the transmissionrate per connection will be 16 kbit/s. For half-rate traffic channelsthe transmission rate is 8 kbit/s per connection. A transcoder/rateadapting unit TRAU converts the coded 16 kbit/s or 8 kbit/s digitalinformation to the 64 kbit/s channel, and on this channel the data istransmitted to an IWF unit which is located in the mobile servicesswitching centre MSC and which performs the required modulation and rateconversion, whereupon the data is transmitted to some other network.Thus, the user data is transmitted over fixed connections in the uplinkdirection from base transceiver station BTS to base station controllerBSC and to mobile services switching centre MSC and, correspondingly,the data to be relayed to mobile station MS is transmitted in thedownlink direction from mobile services switching centre MSC throughbase station controller BSC to base transceiver station BTS and fromthere further over the radio path to mobile station MS.

[0004] In the GSM system, a Channel Codec Unit, CCU, of the basetransceiver station performs a conversion of the signal received on theradio channel to the PCM time slot channel of the trunk line runningover the A bis interface and a conversion of the frame structure of thesignal received over the A bis interface into a form which can betransmitted on the radio channel. The transcoder unit TRAU performs theconversion operations on the signals to be transmitted across theA-interface. The transcoder/rate adapting unit TRAU is often located farfrom the base transceiver station, e.g. in connection with the basestation controller BSC.

[0005] In a digital mobile system, speech is generally coded into adigital form by using low rate speech coding. Nowadays the SM systemuses Full Rate FR coding at a transmission rate of 13 kbit/s, Half RateHR coding at a transmission rate of 5.6 kbit/s, Enhanced Full Rate EFRcoding at a transmission rate of 12.2 kbit/s and Enhanced Half Rate EHRcoding. The enhanced speech codings are so advanced that the quality ofspeech is not significantly reduced in them.

[0006] Thus, speech coding is performed in the mobile station and on themobile network side in the transcoder unit TRAU. The speech informationto be transmitted is one of the parameters of the speech coding method.In modern GSM systems the TRAU transcoders are of several differenttypes of coding, e.g. full rate, half rate or double acting, which isable to change from one rate to another. The transcoders convert thespeech from a digital format into another, e.g. they convert 64 kbit/sA-law PCM arriving from the exchange over the A interface into 13 kbit/sfull rate FR coded speech for transmission to the base transceiverstation line, and vice versa. In a call between two mobile stations PCMspeech samples are transmitted from one transcoder to another, whichcodes them by a speech coding method which is used on the radio path.Repeated coding and decoding of the speech signal during thetransmission will distort the speech signal, for which reason thiscoding-decoding chain, which is called tandem coding, is usuallyavoided.

[0007] The Finnish Patent Application FI-951807 presents transmission ofspeech frames, which have not been decoded, between transcoders and thusbarring of tandem coding in the transcoder, when the call is one betweentwo mobile stations, that is, a Mobile to Mobile Call, MMC. In thesolution according to the application, the coded speech parameters aresent on the PCM time slot sub-channel without any decoding and coding inthe TRAU transcoders of the mobile station network. Tandem coding isavoided by relaying with minor changes the frames coming from one basetransceiver station BTS through these tandem connected TRAU transcodersto another base transceiver station BTS. The receiving transcoder willperceive from these minor changes in the frame that coding need not bedone, and it will relay further the received speech parameters of theframe as such.

[0008] The Finnish Patent Application FI-960590 presents a transmissionadaptation for a connection between exchanges. In the solution accordingto the application, a speech signal is transmitted coded by a speechcoding method on a sub-channel of a PCM channel. The speech coding forthe connection between exchanges is chosen according to the speechcoding of the TRAU frames of the A-interface, except if the speechcoding of the TRAU frames received from the A-interface is differentfrom the speech coding of TRAU frames received from other transmissionequipment, that is, if the parties to the call are using differentspeech codings. FIGS. 2a-2 c illustrate this adaptation of thetransmission for a connection between exchanges in a few cases shown asexamples. The speech coding used in each part of the transmission pathis marked in the figures, in this example they are full rate FR and halfrate HR speech coding. In FIG. 2a both mobile stations MS1 and MS2 usethe full rate FR speech coding method. Hereby the speech parameters aretransmitted through the mobile station network as unchanged full ratespeech parameters. In FIG. 2b both mobile stations MS1 and MS2 use ahalf rate HR speech coding method. Hereby the speech parameters aretransmitted through the mobile station network as half rate speechparameters. In the case shown in FIG. 2c, mobile station MS1 uses halfrate HR speech coding while mobile station MS2 uses full rate FR speechcoding. In this situation, a change is made at the mobile servicesswitching centre MSC1 end to full rate speech coding and the necessarydecoding and speech coding are performed.

[0009] A problem with the presented transmission situations is the needof transmission capacity, especially on the transmission connectionbetween the base transceiver station and the network transcoder. Thetransmission in the mobile station network of speech parameters of themobile station using full rate speech codec requires a full ratechannel, which cannot be transmitted, if on the transmission connectione.g. only a half of that transmission capacity is available, which isrequired by a full rate signal.

BRIEF SUMMARY OF THE INVENTION

[0010] The purpose of this invention is to boost data transmissionespecially in transmission connections on the network side of a mobilecommunications system.

[0011] This objective is achieved with the method and arrangementaccording to the invention, which are characterised by the featuresstated in the independent claims. Advantageous embodiments of theinvention are presented in the dependent claims.

[0012] The invention is based on the idea that the data communicationsnetwork uses at least in a part of the transmission path between a fixedstation, e.g. a base transceiver station, and a transcoder unit a lowertransmission rate speech coding than the transmission rate of the speechcoding used on the transmission path between the fixed station and theterminal equipment. The speech parameters received from the terminalequipment are converted to the speech coding method used in thetransmission connection between the fixed station and the transcoderunit, and vice versa. In the transcoder unit of the network it ispossible to convert speech parameters received from the terminalequipment back to e.g. the speech parameters of the speech coding usedon the transmission path between the terminal equipment and the fixedstation.

[0013] It is an advantage of such boosting of data transmission thatless transmission capacity is needed per speech connection at least in apart of the transmission connection between the base transceiver stationand the transcoder unit of the network.

[0014] It is another advantage of the data communications systemaccording to the invention that it allows trafficking between terminalequipment using different speech coding methods, at best with only onespeech coding during the transmission.

LIST OF FIGURES

[0015] The invention will now be described in greater detail inconnection with advantageous embodiments and referring to the examplesin accordance with FIGS. 3-6 b in the appended drawings, wherein:

[0016]FIG. 1 shows such parts of a mobile communications network whichare essential to the invention;

[0017]FIGS. 2a-2 c show examples of state-of-the-art speech transmissionsituations;

[0018]FIG. 3 is a speech transmission diagram of data transmissionboosting according to the invention;

[0019]FIGS. 4a and 4 b show speech transmission situations according toa first embodiment of the invention as examples;

[0020]FIGS. 5a and 5 b show speech transmission situations according toanother embodiment of the invention as examples; and

[0021]FIGS. 6a and 6 b show flow charts of data transmission boostingaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention may be applied in connection with anytelecommunications system. The invention will be described hereinafterby way of example and mainly in connection with a digital GSM mobilecommunications system. FIG. 1 shows the simplified structure of the GSMnetwork described above. The interested reader will find backgroundinformation as regards a more detailed description of the GSM systemfrom GSM recommendations and from the book “The GSM System for mobileCommunications”, M. Mouly & M. Pautet, Palaiseau, France, 1992, ISBN:2-9507190-0-7.

[0023]FIG. 3 shows boosting of data transmission in a mobilecommunications system in accordance with the invention. In the caseshown as an example in FIG. 3, the mobile station MS uses full ratespeech coding. Hereby speech parameters of full rate FR speech codingare transmitted between base transceiver station BTS and mobile stationMS. According to the invention, the speech parameters are converted fora transmission connection between base transceiver station BTS and thenetwork transcoder unit TRAU into speech parameters of speech coding ofa lower transmission rate, in the case shown in FIG. 3 into speechparameters of half rate speech coding. Thus, the speech parametersreceived from the mobile station are decoded at the end of basetransceiver station BTS and a new speech coding is carried out by aspeech coding method of a lower transmission rate, in the case shown inFIG. 3 by half rate speech coding. The new speech parameters thusobtained are transmitted over the transmission connection to thetranscoder unit TRAU. Correspondingly, the speech parameters receivedfrom transcoder unit TRAU are decoded at the end of base transceiverstation BTS and a new speech coding is performed by a speech codingmethod available on the radio path, in the case shown in FIG. 3 by fullrate speech coding. The resulting speech parameters are transmitted tomobile station MS over the radio path. When required, a correspondingconversion of the speech parameters is performed at the end oftranscoder unit TRAU to transmit speech elsewhere in the network andfrom elsewhere in the network to the base transceiver stationconnection. From transcoder unit TRAU the speech is transmittedelsewhere in the network in some state-of-the-art manner. Instead of thespeech codings shown in FIG. 3 other speech codings may also be used,however, so that the speech coding in use in the connection between thebase transceiver station and the transcoder unit is a speech coding of alower transmission rate than the speech coding used on the radio path.

[0024] In the following the invention will be described in greaterdetail in the light of a first embodiment of the invention and referringto FIGS. 4a and 4 b. In the first embodiment of the invention, a speechcoder 45 according to the invention is located when required inconnection with base transceiver station BTS to decode and recode thecall to be relayed so that the speech parameters to be transmitted areconverted between a first and a second speech coding method. FIG. 4ashows a call transmission connection between two mobile stations MS1 andMWS2 as an example. Mobile station MS1 uses enhanced full rate speechcoding EFR and mobile station MS2 uses enhanced half rate speech codingEHR. Base transceiver station BTS1 receives the EFR speech parametersfrom mobile station MS1. The speech coder according to the inventiondecodes them and recodes by enhanced half rate speech coding EHR. TheseEHR speech parameters are transmitted through base station controllerBSC1 to transcoder unit TRAU1 and from there further by usingstate-of-the-art barring of tandem coding as EHR speech parameters byway of exchanges MSC1 and MSC2 to transcoder unit TRAU2, which transmitsthe EHR speech parameters further through base station controller BSC2to base transceiver station BTS2. At the end of base transceiver stationBTS2 the EHR speech parameters are transmitted over the radio path tomobile station MS2, where enhanced half rate speech coding EHR is used.Thus, in the speech transmission described above, only one decoding andrecoding of speech coding is performed on the mobile station networkside. Correspondingly, the EHR speech parameters received from mobilestation MS2 are transmitted unchanged over the transmission network tothe end of base transceiver station BTS1, where a speech coder accordingto the invention decodes them and carries out recoding by enhanced fullrate speech coding. These EFR speech parameters are transmitted frombase transceiver station BTS1 over the radio path to mobile station MS1.

[0025]FIG. 4b is an example of another situation showing a calltransmission connection between two mobile stations MS1 and MS2 whereboth mobile stations MS1 and MS2 use enhanced full rate speech codingEFR. Base transceiver station BST1 receives the EFR speech parameterssent by mobile station MS1. In order to boost the data transmission onthe connection between the base transceiver station and the networktranscoder unit, the speech coder according to the invention decodes thespeech parameters received at base transceiver station BTS1 and recodesthe speech by enhanced half rate speech coding. The resulting EHR speechparameters are transmitted to transcoder unit TRAU1, which againtransmits the EHR speech parameters unchanged through exchanges MSC1 andMSC2 to transcoder unit TRAU2. TRAU2 sends the EHR speech parameters tobase transceiver station BTS2. Before being transmitted onto the radiopath, the received EHR speech parameters are decoded in a speech coderaccording to the invention and they are recoded by the enhanced fullrate speech coding available on the radio path. The EFR parameters aretransmitted to mobile station MS2. Correspondingly, the same procedureis used for the EFR speech parameters of mobile station MS2 which arereceived at base transceiver station BTS2.

[0026]FIGS. 5a and 5 b show examples of situations in accordance withanother embodiment of the invention. In this second embodiment of theinvention a first speech coder 45 is located in connection with the basetransceiver station, besides which another speech coder 55 is located inconnection with transcoder TRAU also to decode and recode the speech tobe relayed so that the speech parameters are converted between a firstand a second speech coding method. FIG. 5a shows a speech transmissionconnection between two mobile stations MS1 and MS2, when both mobilestations use enhanced full rate speech coding. The EFR speech parametersreceived by base transceiver station BTS1 from mobile station MS1 areconverted in accordance with the invention into EHR parameters and theyare transmitted to transcoder unit TRAU1 in the same manner as wasdescribed above in connection with the first embodiment of theinvention. The EHR speech parameters received in transcoder unit TRAU1are converted in a speech coder in accordance with the invention for atransmission rate of enhanced full rate speech coding. When required,the speech parameters may also be converted into PCM samples. At thetransmission rate of enhanced full rate speech coding the speech istransmitted from transcoder unit TRAUL through exchanges MSC1 and MSC2to transcoder unit TRAU2. The speech received in transcoder unit TRAU2is converted in a speech coder according to the invention back to EHRspeech parameters, which are transmitted to base transceiver stationBTS2. Before being transmitted onto the radio path, the EHR speechparameters are converted in accordance with the invention into EFRspeech parameters, as was described above in connection with a firstembodiment of the invention.

[0027]FIG. 5b shows an example of another situation where mobile stationMS1 uses enhanced full rate speech coding EFR and mobile station MS2uses enhanced half rate speech coding EHR. The EFR speech parametersreceived at base transceiver station BTS1 are converted in accordancewith the invention into EHR speech parameters and they are transmittedto transcoder unit TRAU1 in the same manner as was presented above inconnection with the description of FIG. 4a. The EHR speech parametersreceived in transcoder unit TRAUL are converted in a speech coderaccording to the invention into a transmission rate of enhanced fullrate speech coding. When required, the speech parameters may also beconverted into PCM samples. At the transmission rate of enhanced fullrate speech coding the speech is transmitted from transcoder unit TRAU1through exchanges MSC1 and MSC2 to transcoder unit TRAU2. The speechreceived in transcoder unit TRAU2 is again converted in a speech coderaccording to the invention into EHR speech parameters, which aretransmitted to base transceiver station BTS2 and from there further overthe radio path to mobile station MS2. The EHR speech parameters receivedfrom mobile station MS2 are converted correspondingly in a reversedorder when transmitting the speech in the network from base transceiverstation BTS2 to base transceiver station BTS1.

[0028]FIG. 6a shows boosting of data transmission in accordance with theinvention in a mobile communications system in the uplink direction. Atpoint 602 the transmission rate is determined which is to be used on thetransmission path between the base transceiver station and thetranscoder unit, and at point 604 the transmission rate of speechparameters received from mobile station MS at the base transceiverstation is determined, that is, the transmission rate used on the radiopath. At point 606 the transmission rates determined above are comparedwith one another. If the radio path transmission rate is higher than thetransmission rate of the transmission path between the base transceiverstation and the transcoder unit, the speech parameters are decoded(point 608) and they are recoded by the second speech coding, which isused on the transmission path between the base transceiver station andthe transcoder unit (point 610). The speech parameters thus processedare transmitted from the base transceiver station to the transcoder unitover the transmission path (point 612). If in the check at point 606 theradio path transmission rate is not higher than the transmission rate ofthe transmission path, then the speech parameters are processed in astate-of-the-art manner and they are transmitted further in the network.

[0029]FIG. 6b shows boosting of data transmission in accordance with theinvention in a mobile communications system in the downlink direction.At point 622 the transmission rate used on the radio path is determined,while at point 624 the transmission rate of speech parameters receivedfrom the transcoder unit at the base transceiver station are determined.At point 626 a comparison is made between the transmission ratesdetermined above. If the transmission rate used on the transmission pathbetween the base transceiver station and the transcoder unit is lowerthan the transmission rate of the radio path, then the received speechparameters are decoded (point 628) and they are recoded by a firstspeech coding, which is used on the radio path (point 630). Thereprocessed speech parameters are transmitted from the base transceiverstation to the mobile station over the radio path (point 632). If it isfound in the check at point 626 that the transmission rate of thetransmission path is not lower than the transmission rate of the radiopath, then the speech parameters are transmitted to the mobile stationin a state-of-the-art manner.

[0030] The speech coder in accordance with the invention supports two ormore speech coding methods, which are used in a telecommunicationssystem, preferably in a mobile communications system. The speech coderaccording to the invention may also be used in other situations thanthose shown in the preceding examples to implement the functionalityaccording to the invention.

[0031] In mobile station MS speech coding and decoding are performed ina state-of-the-art manner, which is why it is not described in greaterdetail in this connection.

[0032] The drawings and the related explanation are intended only toillustrate the inventive idea. As regards its details the boosting ofdata transmission in accordance with the invention may vary within thescope of the claims. Even though the invention was described abovemainly in connection with a mobile communications system, the boostingof data transmission may be used also for a telecommunications system ofsome other kind, when the telecommunications system uses a lowtransmission rate speech coding on the transmission path between thefixed station and the terminal equipment. Thus, in the presentapplication a base transceiver station means any such unit in atelecommunications network which is in connection with pieces ofterminal equipment, whereas a mobile station means both mobile and fixedpieces of terminal equipment which are in connection with atelecommunications network. The functionality according to the inventionmay be implemented in the network for all connections or for someconnections only.

1. Method for boosting data transmission in a telecommunications systemincluding at least one fixed station (BTS), pieces of terminal equipment(MS), which over a first transmission path are in connection with thefixed station, at least one transcoder unit (TRAU) on thetelecommunications network side and a second transmission path betweenthe fixed station (BTS) and the transcoder unit (TRAU), whichtelecommunications system on the first transmission path uses a firstspeech coding method, which is a low transmission rate speech coding,characterized in that in the method at least on a part of the secondtransmission path a second speech coding method is used, which is speechcoding at a lower transmission rate than the first speech coding, andthe speech parameters received from the terminal equipment fortransmission onto the second transmission path are converted into speechparameters of the second speech coding method and the speech parametersto be transmitted to the terminal equipment on the first transmissionpath are converted into speech parameters of the first speech codingmethod.
 2. Method as defined in claim 1, characterized in that inconnection with the fixed station (BTS) the speech parameters to betransmitted onto the second transmission path are converted into speechparameters of the second speech coding method and the speech parametersreceived from the second transmission path are converted into speechparameters of the first speech coding method.
 3. Method as defined inclaim 2, characterized in that the speech parameters to be transmittedonto the second transmission path are converted into speech parametersof the second speech coding method and the speech parameters receivedfrom the second transmission path are converted for the transmissionrate of the first speech coding method.
 4. Method for boosting datatransmission in a mobile communications system including at least onebase transceiver station (BTS), at least one transcoder unit (TRAU) onthe mobile communications network side, a transmission path betweenthese and mobile stations (MS) which over the radio path are inconnection with the base transceiver station, which mobilecommunications system on the radio path uses a first speech codingmethod, which is a low transmission rate speech coding, characterized inthat in the method at least on a part of the transmission path a speechcoding method is used which is speech coding at a lower transmissionrate than the first speech coding, and the speech parameters receivedfrom the mobile station for transmission onto the transmission path areconverted into speech parameters of the second speech coding method andthe speech parameters to be transmitted to the mobile station on theradio path are converted into speech parameters of the first speechcoding method.
 5. Method as defined in claim 4, characterized in thatthe speech parameters to be transmitted onto the transmission path areconverted into speech parameters of the second speech coding method andthe speech parameters received from the transmission path are convertedfor a transmission rate of the first speech coding method. 6.Arrangement for boosting data transmission in a telecommunicationssystem including at least one fixed station (BTS), pieces of terminalequipment (MS), which over a first transmission path are in connectionwith the fixed station, at least one transcoder unit (TRAU) on thetelecommunications network side and a second transmission path betweenthe fixed station (BTS) and the transcoder unit (TRAU), whichtelecommunications system on the first transmission path uses a firstspeech coding method, which is speech coding at a low transmission rate,characterized in that the arrangement includes in a telecommunicationsnetwork at least one first speech coder for converting speech parametersto be transmitted between the first and the second speech coding method,which second speech coding method is used on the said transmission pathon the transmission connection between the speech coder and thetranscoder unit and it is speech coding at a lower transmission ratethan the first speech coding.
 7. Arrangement as defined in claim 6,characterized in that the first speech coder is located in connectionwith the fixed station (BTS).
 8. Arrangement as defined in claim 6,characterized in that the arrangement includes in a telecommunicationsnetwork at least one second speech coder for converting speechparameters to be transmitted from one speech coding method into thesecond method so that the second speech coding method is used on thesaid transmission path on the transmission connection between the firstspeech coder and the second speech coder.
 9. Arrangement as defined inclaim 8, characterized in that the second speech coder is located inconnection with the transcoder unit (TRAU).
 10. Mobile communicationssystem including at least one base transceiver station (BTS), at leastone transcoder unit (TRAU) on the mobile communications network side, atransmission path between these and mobile stations (MS), which over theradio path are in connection with the base transceiver station, whichmobile communications system on the radio path uses a first speechcoding method, which is a low transmission rate speech coding,characterized in that the mobile communications system includes at leastone first speech coder for converting speech parameters to betransmitted between a first and a second speech coding method, whichsecond speech coding method is used on the said transmission path on thetransmission connection between the speech coder and the transcoder unitand it is speech coding of a lower transmission rate than the firstspeech coding.
 11. Mobile communications system as defined in claim 10,characterized in that the first speech coder is located in connectionwith the base transceiver station (BTS).
 12. Mobile communicationssystem as defined in claim 10, characterized in that the mobilecommunications system includes in a mobile communications network atleast one second speech coder for converting speech parameters to betransmitted from one speech coding method into a second method so thatthe second speech coding method is used on the said transmission path onthe transmission connection between the first speech coder and thesecond speech coder.
 13. Mobile communications system as defined inclaim 12, characterized in that the second speech coder is located inconnection with the transcoder unit (TRAU).